Wearable devices are increasingly popular because they can better meet people's communication needs. This reflects a development trend that future communications devices are becoming smaller and more portable. Currently, major communications device manufacturers have released their own smartwatches, and there is fierce competition in this field.
Compared with common watches, smartwatches integrate a communication function and therefore need a built-in antenna to transmit or receive electromagnetic signals. Currently, an antenna is usually disposed around a printed circuit board in a form of a monopole, an inverted-F antenna (IFA), or the like. To maintain good transmit efficiency, the antenna needs headroom. There is a specific height from the disposed antenna to the printed circuit board.
However, the headroom required by the antenna increases a size of a wearable device (such as a smartwatch). This is unfavorable for miniaturization of the wearable device. In addition, when an antenna such as a monopole or an IFA approaches a human body, a relatively large amount of electromagnetic waves emitted by the antenna is absorbed by the human body. This causes performance of the antenna to greatly deteriorate and is harmful for human health. More functions are integrated into a wearable device, and communication functions need to integrate functions of BLUETOOTH, a wireless local area network, a communications system, and a global positioning system. Correspondingly, different antennas are required to transmit or receive signals of these functions. However, a wearable device is usually small and unable to accommodate these antennas.